Sudden infant death syndrome (SIDS) is the leading cause of postneonatal infant death in the United States. About 7,000 deaths occur each year from SIDS. In addition, many infants die each year of asphyxiation while in a crib.
SIDS is defined as the sudden death of an infant under 1 year of age that remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history.
Prone sleeping is associated with spontaneous face-down sleeping in infants. The face-down position is associated with rebreathing expired gases, including carbon dioxide, and increased carbon dioxide lung pressure in normal infants. In some cases the amount of rebreathed carbon dioxide is sufficient to cause death in normal infants. B. A. Chiodini and B. T. Thach, Impaired ventilation in infants sleeping facedown: Potential significance for sudden infant death syndrome, J. Pediatrics, Vol. 123, 686 (1993); J. S. Kemp and B. T. Thach, Sudden Death in Infants Sleeping on Polystyrene-Filled Cushions, New England Journal of Medicine, Vol. 324, 1858 (1991). In that case the cause of death is asphyxiation, not SIDS. However in SIDS's cases the rebreathing of carbon dioxide, short of asphyxiation, may be a contributing cause of death of the infant.
A brain defect has been discovered that may be the cause of some cases of SIDS. H. C. Kinney, J. J. Filiano, L. A. Sleeper, F. Mandell, M. Valdes-Dapena, W. F. White, Decreased Muscarinic Receptor Binding in the Arcuate Nucleus in Sudden Infant Death Syndrome, Science, Vol. 269, 1446 (1995). That study suggests that a normal infant's nervous system detects progressive hypercarbia (excessive carbon dioxide in the blood) and asphyxia (stoppage of breathing) and responds by arousal and a series of protective reflexes to ensure airway patency whereas the SIDS infant having the defect does not perform these protective reflexes. The present invention compensates for this brain defect by continuously removing expired carbon dioxide from the crib and providing fresh room air to stimulate breathing. This compensation occurs for all facial positions including face-down.
Other studies have shown an association between excessive clothing and beddings and an increased rate of SIDS. W. G. Guntheroth, P. S. Spiers, Sleeping Prone and the Risk of Sudden Infant Death Syndrome, JAMA, Vol. 267, No. 17 (1992). It is believed that excessive clothing and bedding produces hyperthermia (overheating) within the infant.
The American Academy of Pediatrics recommends that an infant be placed on its back or side when sleeping because the incidence of SIDS is greatly reduced as compared to the prone position. American Academy of Pediatrics, Positioning and SIDS, Pediatrics, Vol. 89, No. 6 (1992). However, when the infant is three to four months old it is capable of rolling over to the prone position. The supine position is considered particularly unsafe for infants suffering from respiratory distress or excessive regurgitation after feeding.
Pediatricians recommend use of a firm mattress and the avoidance of unduly soft beddings. It is believed that such measures will prevent the infant from sinking into the mattress and beddings and thereby avoid restricting the availability of ventilation and oxygen.
Periodic breathing is a normal phenomenon in which an infant's breathing is interrupted by recurrent apneas (absences of breathing). It has been shown that an increase in ambient oxygen concentration reduces the incidence of apnea in infants. J. Kattwinkel, Neonatal/Apnea: Pathogenesis and Therapy, J. Pediatrics, Vol. 90, 342 (1977) ; T. Hoppen-Brouwers, J. E. Hodgman, R. M. Harper et al., Polygraphic studies of normal infants during the first six months of life: I.V. Incidence of Apnea and Periodic Breathing, Pediatrics, Vol. 60, No. 418 (1977); N. N. Finer, K. J. Barrington, B. Hayes, Prolonged Periodic Breathing: Significance in Sleep Studies, Pediatrics, Vol. 89, No. 3 (1992). Those sleeping infants who are not aroused by increases in oxygen level (hypoxic arousal) were determined to have a greater risk of SIDS. Perhaps excessive rebreathing of carbon dioxide has an anesthetic effect on the sleeping infant which can be overcome in most cases by increasing the ambient oxygen level.
While no specific cure of SIDS is known, the above studies as well as other medical research suggests that neurological disorders, sleeping in the prone position, rebreathing expired carbon dioxide and overheating may each be a contributing cause.
Since almost all cases of SIDS and asphyxiation occur in cribs, it is reasonable to investigate the characteristics of the crib system consisting of the infant, clothing, mattress, beddings and bumper pads in order to determine whether some of these system components, excluding the infant, are contributing environmental causes of SIDS and asphyxiation.
The U.S. Consumer Product Safety Commission (CPSC) has studied rebreathing of carbon dioxide using rabbits as well as a doll in combination with a mechanical lung. N. J. Scheers, Infant Suffocation Project, Final Report, U.S. Consumer Product Safety Commission, January, 1995. In those studies the amount of rebreathing of carbon dioxide was measured for a variety of infant bedding items. The test included death scene re-creations. It was found that expired carbon dioxide enters infant bedding and provides a "pool" of carbon dioxide for rebreathing. The results showed that rebreathing carbon dioxide trapped in soft bedding products may have contributed to the deaths of the estimated 30 percent of infants found in potentially suffocating circumstances. In addition, the CPSC recommended against use of decorator pillows or the like in the crib environment to further lessen the likelihood of suffocation.
Prior art devices for reducing the likelihood of SIDS usually focus on an infant's respiration and attempt to provide oxygen to the infant while removing expired carbon dioxide efficiently. In other words, they attempt to increase ventilation within the crib. It is known that conventional bedding is minimally gas permeable and causes "pooling" of potentially dangerous expired carbon dioxide within the beddings for rebreathing.
One such device is disclosed in U.S. Pat. No. 5,389,037 to Hale. The Hale apparatus includes an air plenum assembly, including an electric blower, attached to the crib to mechanically direct a flow of air toward the infant. Still another device is disclosed in U.S. Pat. No. 5,317,767 to Hargest et al. In that device, air is directly introduced into the crib environment through an air permeable mattress upon which the infant rests. Yet another device is disclosed in U.S. Pat. No. 5,305,483 to Watkins which describes a mattress pad whereby the pillow portion is provided with a pump and ventilation means to constantly pump air through numerous air pockets supplied within the pad.
Each of these devices is complex, requires an electric power source, is noisy and obtrusive and may be uncomfortable for the infant. Further, the Hargest and Watkins devices require supplemental supports positioned underneath their pads since the air permeable pads are neither rigid nor self-supporting. Hale's apparatus may be ineffective if the infant's nose and month are covered by the mattress and/or beddings so that air blown toward the infant has no effect on respiration.
A need has existed within the art for a sleeping pad that will provide passive ventilation of the crib without requiring pumps, fans or other potentially hazardous electrical devices. In addition, it is desirable to provide a sleeping pad that will sufficiently remove carbon dioxide and mucus or other fluid spit up by the child when sleeping thereby reducing the risks of SIDS and asphyxiation. Lastly, it is desirable to provide a sleeping pad, crib slat bumpers and gas and liquid transmissive bedding for use in a crib to enable: (a) expired respiratory gases to move away from the crib; (b) increase ventilation to the crib to reduce the risk of overheating and (c) supply sufficient oxygen to the crib to stimulate breathing.